damp proof course

[h12rpo]

Silly question time:

When putting a layer of damp proof membrane in the base wall, is it sandwiched by the mortar or laid on top of the blocks dry and then a bed of mortar .......?

[bookemdanno]

Thats not a silly Q R2-D2.
You should sandwich the DPC between layers of mortar. The DPC should have a criss-cross pattern on it. This is to give it some element of grip. Look at your house, along the line of the bottom of door frames and you should see a slightly thicker layer of mortar with a black line running through it. Thats the DPC.

[h12rpo]

Since i was going to use the blue poly membrane that i used for my base, i wouldnt have any criss cross pattern on it though

Also i've seen on the fb forum that somebody recommended no bed of mortar for the first soldier course......that seems to me a bit strange ..........any observations???

[conic]

blue plastic membrane is fine because theweight of the brick will have enough force to hold it all still.
How I always do it is to first put down a 5mm mortar bed using a 3 sand and 1 cement mix then lay your membrane on top and put another 10mm on top then lay your bricks.
Make sure the membrane is cut off and does not s further than the mortar line of it will suck the rain in.

depending if you like the new look or the rustic look should make your decision on havv ing the membrane. I left it off my oven as I already had a good membrane under my concrete slab and was not bothered if i had rising damp but its now been up about 6 years and is perfect.
On the other hand when I built my workshop i did not want to chance any damp so included a membrane onb the damp proof course and that also worked well.

whatever you do, dont stress about it.

conic

[cannyfradock]

I think the book says lay your DPC (damp proof coarse) on a thin bed of mortar, then lay a normal bed of mortar on top of this to start your first course. In reality (on site) the DPC is laid dry and held in place with a few dry bricks until the first course is laid......the only criteria is that if the course below has holes or frogs in the bricks, then they should be filled before laying the DPC. You are laying DPM (damp proof membrane) which is virtually the same thing. DPM is 1200gauge and comes in a large roll 4 meters wide and DPC is the same thickness and comes in a rather smaller roll of 4, 6, 9 or 18 inches wide.

...I'm not trying to contradict anything that has been said in previous posts as DPC and DPM ARE different.....but for our needs, a strip of DPM is not going to go slip sliding away with the weight of the walls and the dome on top of it.

Terry